Rheostat.



PATENT-D AUG. l1., i908.

WERT,

RHSTR AWLIGATION FILED JULY 12,1Qo5.

No: 39mm 3SHEETS-SHEET i PATENTED AUGK ll, 1908,

s SHBMMSBM a,

WIRT.

RH'BOSTA' AFPLIGATIQN FILED JULY 12,1905.

'NETE @TATES PATENT CHRLES WIRT, OF PHILADELPHIA, PENNSYL'YANA, ASSIGNORTO CHARLES WRT AND COMPANY, C-F NEWARK, NEW JERSEY, A CORPORATION OF NEWJERSEY.

RHEOSTAT.

Specification of Letters Patent.

latented Aug.' l1, 1903.

Application filed July l2, 1905. Serial No. 269,324.

To all whom it may concern:

Be it known that I, CHARLES VVIRT, a c.it izen of the United States,residing at Philadelphia, Pennsylvania, have invented a certain new anduseful Improvement in Rheostats, of which the following is adescription."

l the characteristics of durability with capaeity to stand a high `rateof work in proportion to size andweight, and also to Withstand a hightemperature without injury. o

' ln the accompanying drawings is shown a rheostat which for the salieof clearness omits parts not needed to show the particular constructionand method of maintenance, Also for the sake of clearness is shown avery heavy resistance conductor having few turns and connected to butfew contact blocks. Commercial rheostats would have more steps or blocks'in the commutator and a longer, lighter resistance conductor placed orwound into more turns Figure l shows a top View of a rheostat embodying-the invention, the shaft and.

handle broken oil, `Fig. 2 shows a side View of the same; liig. 3 showsa bottom plan View; and Fig. 4 u. iid section through the center line ofthe central shaft or spindle, Fig. 5 shows one conmiiitator block; aconl necting rod, and an envelop or contact clip. Fig. 6 illustratesratherv diagraniinatically a rellexed. wire Vhaving uniform pitch7 orloop spaces. ywire in which the pitch or loop spans meas ured in thedirection of the completed strip continuously decrease, thus giving theeffect of increasing resistance per unit of length while retaining theadvantage of using an inexpensive material of uniform section andavoiding joints. Fig. 8 shows a plane spiral and illustratesdiagrainmatically the plan of arrangement of the resistance conductorwhen coiled into a suitable shape for a round plate (disk) rheostat.Fig. 9 is a view of a modified form of resistance. Fig. 10 is a bottomview, and Fig. l1l is a side elevation of `a modified form of envelop.

In all of the several views like parts are designated bj.' lhe samereference el. meters.

Referring io the rheestat illustrated herein the general description isas follow F ig. 7 shows asimilar reflexed.u

The rheostat consists of a resistance con ductor 1 (formed preferably ofa wire reflexed or put into zig-Zag shape) wound cireularly upon itselflike a roll of tape, the turns being separated electrically by two cordsor strips 2, 3. With each turn there is slipped over the resistanceconductor a sheet metal envelop or clip 4. so as to straddlo theresistance,l

this envelop preferably having an area as large as permissible and nottoo stili; to h down on both sides in close electrical contact .y

This extends with the resistance conductor. beyond the fiat face of thecompleted roll to serve a point of attachment for a eontact with thatsection of the resistance. lnstead of an envelop straddling theresistance conductor, the clip may be secured to one side, or it maystraddle the conductor, but only one end may protrude beyondthe'supporting body.

found with the resistance and separating the turns thereof are the twothreads or strips of flexible insulating material 2, 3. These serve asan insulation; also as spacing stri s to give the desired external'dimension to t e (i 7) 1 i roll. rllie thickness of tnese strips wouldhe predetermined, as the temperature limit of any rheostat is generallyi'ixed, and to keep within such linut for a given duty a certain sizewill be called for as a minimum. In the construction shown, a very lightweight of conductor may be used, keeping down the cost of the mostexpensive ite-in in the ordinary cost of the material; and havingpredetermined the desirable size of the structure to fill that spacewith the resistance material disposed in an extended manner, iilling theinterspace with a material 5 having the qualities of insulation,solidity, and, so far as ossible, both heat .capacity and heatoonductivity. This material constitutes a molded supporting body.rilhere are materials of the description of artificial stone, alsoinsulating materials in use which may be molded iii the soft state,pressed into sha e, or even poured in a semi-liquid form, whic i fuhilthe requirements.

Having the resistance put into the required form with the Contactenvelope located as required and extending atene side, it is onlyrequired to place these parts on a` flat surfae or into the bottom 'of asuitable temporary or permanent ease or box, place the cominutator bars6-the sleeve 7 for spindle--the inclosing metal ring-the feet 8-S, &e.,and ll in a liquid or semi-liquid insulating body to embed all theseparts in a block which is later to become solid. Any suitable materialfor this purpose may be used, but preferably a material which does notrequire a very high temperature either to liqueiy or to harden.. numberol patents on plastic compositions describe a great variety of suchmaterials, some o'l' which haye good insulating qualities. A gig or'form may be used to locate the respective parts in correct relativeposition while the iilling is being applied.

Agtter the completion oi" the body of the 5`1`heostat by thesoliditieation oll they insulating block the connection ot theresistance sections to the eommutator blocks may be completed by placingthe wires .)-.l. As shown, these wires or rods are held at either end bybeing forced into slots in. the commutator and clips.

The resistance conductor is arranged in the iorm of a [lat spiral asshown in Fig. S and the connections 4 are taken at intervalsprogressively 'from that conductor. 'l`he result ol' this arrangement isthat the conductor and the insulatingl body in which it is embedded areheated pri lessively in rings or annular Zones, instead ol by angularsectors as heretofore in disk rheostats. This re- Suits in a moreunii'orm heating and a lower maximum temperature. vWhile the connections4 are arranged in a spiral the commutator blocks (i are arranged 'in acircle, thus enabling the employment ol' a contact arm pivoted at thecenter olI the disli, which contact arm can be made short il` thecomunitator blocks are. located within the innermost turn ol' theresistance conductor as they prelerably are.

Fig. t) illustrates a i'orm ot' resistance lstrip in which theinsulating threads 2,' 3 'form the warp and the resistance wire i theWett ol a l'abrie which is woven in the ordinary manner like. a tape orribbon. As in the construction shown the linal supportl and insulationis allorded by a heat resisting body, it is not required that theinsulating strips or threads applied to or laid withthe vresistanceconductor should be lire proolI or heat resisting. l`he ellectiveness orlit'e, ol' the rheostat would not be reduced by any heat effect thatcould be inoduced under Commercial conditions on (lor example) cottonthreads or strips ill used as shown.

Figs. 1() and 11 show a modification in which the sheet metal envelop 4is extended to reach and overlap the end ol the commutator block. 'lherheostat may be wound With a resistance conductor in the l'orm olI aflat tape or ribbon. 'lhis would sacrilice the binding etl`ect ol thewire loops, which embedded in the insulating` body act to reinl'orce thestrength oll the latter' in a way that a smooth Ilat strip could not.

'lhe commutator is preferably formed ol metal segments, each having ahollow' central chamber lt), and a projecting l'oot l1'. rlhe centralchamber will become [illed with the molded supporting material, and willthereby become [irmly anchored in place. 'l`he projecting l'oot extendsbeyond the tilling (indicated by dot-ted line llig. 4) and is providedwith a notch 12, within which the connector is l'orced. The parts maythereby be held iu position without the use ol` screws or solder. lheconnectors are outside oi the body, as shown, and may be adjusted orremoved, as desired, without demolishing the apparatus.

llaving now described my invention what l claim :ne and desire to secureby lietters Patent is i. ln a rheostat, the combination ol a resistanceconductor, contact blocks and a hub or support for the moving element,with a molded body of insulation forming the body ol the rheostat and inwhich the resistance conductor, contact blocks and hub or support lorthe moving element are embedded and mechanically held by the setting orhardening oll the molded insulating body around them, substantially asset forth. l

2. Ina rhcostat, the combination of a resistance conductor, contactblocks and a hub or support for the moving element, with a molded bodyol insulation.forming the body of the rheostat and in which theresistance. Iconductor, contact blocks and hub or support lor the.moving` element are embedded and meclumically held by the setting orhardening ol the molded insulating body around them, and a metal ringsurrounding the body ot insulation and held thereon by the setting orhardening of such body, substantially as set forth. i

3. A rheostat having a spit-ally wound resistance, and a commutatorinside of the resistance, both resistance and conunutator being within amolded supporting body, and radial connections between the conm'lutatorand the resistance outside of the body.

4. A rheostat having a spirall wound resistanee, and a commutat'orwithin the spiral, both being within a molded supporting body, envelopsconnecting the resistance at inter'- vals within the body and projectingoutside oli the body, and radial connectors between the envclops and thecommutator.

5. A rheostat having a conunntatorformed otl segments mounted within a.molded su porting body, a resistance Within the body and outside ol' theconunutatm', the said coinmutator having notches in the protrudingportion and radial connectors within the notches, the said connectorsconnecting the resistance.

t'. A rheostat having a coinniutator and a spirally wound resistancewithin a molded supporting body, envelops connected to the I tator andresistance outside of the body.

S. A resistance conductor` Jfor rheostats7 consisting of a rctlexed wirehaving its turns in the saine plane and substantially parallel with eachother.

9. A spirally Wound resistance formed of a reilexed strip of varyingpitch.

10. ln a rheostat, the combination of aspirally Wound resistance formedof a reilexed stri') and envelops straddling the strip at intervals. l

11. ln a rheostat, the combination of a s irally Wound resistance formedof a reexed strip mounted within a molded sugporting body, and envelopsstraddling t e strip at intervals Within the body, the said envelopsprojecting outside of the body.

12. ln a rheostat, the `combination of a spirally Wound resistance'formed of a lreilexed strip mounted Within aniolded su porting body, andenvelops .straddling It .e

strips at intervals Within the body, uthe said 'envelop having notchedextremities which,

project outsideof the body.

13. A resistance for a .rheostat consisting of a conductor reile'xed inthe saine plane Lto form a zig-za Wire, the turns being substantiallypara lel with each other and coiled' ,upon itself to the shape of a llatroll or 'a disk, a body of insulation filling the interspaces Withinsaid resistance and formln a supporting land inclosing body adapte todissipate the heat generated in said resistance. l Y

14. A resistance for a rheostat consistin of awire or strip relexedorzig-zagged an thepiteh or linear space of the loops varying.

in regular progression in such manner as to cause a progressive changein the lengthof wire included per unit length of the efierred stri 1li.A rheosltat consisting of a continuous length of resistance wire, theturns bein substantially parallel With each other coile into (a lat rollor spiral, taps attached thereto at intervals connecting With acommutatorl and an inclosing and 'supporting body'of insulationiillingthe spaces within the vo1 urne ofv said coil and 'formingtherewith a solid body adaptedto dissipate the heat produced, and toprovide re uired 4mechanical su ort and electrical insu ation.

is specification signed and' witnessedi thisl30 day of June, 1905.v

CHARLES WRT;

Witnesses:

JOHN L. Lo'TsoH, SNO Roar. TAYLOR.

